Prime-mover dynamo plants – Electric control – Fluid-current motors
Patent
1984-08-30
1987-02-03
Roskoski, Bernard
Prime-mover dynamo plants
Electric control
Fluid-current motors
290 55, 416145, F03D 704
Patent
active
046410392
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to improvements in wind-powered engines and aerogenerators comprising a rotor with variable-pitch propeller and regulating their speed of rotation by orientation of the wings in the sense of retraction or feathering.
In an aerogenerator of the above type, the axis constituting the pivot of each variable pitch blade lies in the front part of the profile of the blade, at the point of equilibrium of transverse aerodynamic lift thereof, i.e. approximately in the front quarter of the types of profiles used, the latter being defined as having to possess a good stability of this point of equilibrium. Consequently, the section, or the outer length of the outline of the profile of the blade is much greater to the rear of this point of aerodynamic equilibrium, towards the trailing edge, than it is towards the front, towards the leading edge. The rear mass of the blade is therefore much greater than the front mass.
For such a receiving propeller to function, the chord of the profile of each blade must have a helix angle with respect to its plane of rotation. Consequently, the rear and front masses of the profile of the blade are not aligned in the plane of rotation of the rotor, passing through the pivot axis of the blade on itself, but they lie respectively to the rear and in front of this plane. These rear and front masses being unequal and the rear mass being predominant, this results in the existence of an out-of-balance or disturbing rear mass with respect to the front mass of the blade, whatever the speed of rotation of the rotor.
In the event of rotation of the propeller slowing down due to any effect such as a drop in the wind, eddy, delay of regulation reversing the angle of attack of the profile, use of the power of the machine, etc. . . . , such a deceleration creates a disturbing or parasitic force resulting from the kinetic energy of the unbalanced rear mass of the blade. This disturbing force then tends to pivot the blade to a position of feathering with all the consequences of this action.
In particular, in strong wind, the regulation moving away the application of this force and more substantially if the machine is off-load, in the event of slowing down of the wind or of delay of regulation, the propeller slowing down, the disturbing force resulting from the kinetic energy of the unbalanced rear amss of the blade causes this blade to pivot about its axis and brings about a transfer of the lift which converts the previously receiving propeller into an energy-absorbing pushing propeller. Such absorption leads in turn to an increase in the deceleration of the rotor with amplification of the phenomenon until the kinetic energy of the assembly disappears. This phase over, the blades return to face the wind, the propeller starts off again and the phenomenon may then resume.
Such a rapid and sudden change in situation in which the propeller is alternately receiving and pushing, presents the drawback that the machine is not very productive and, in addition, it may cause the rapid destruction thereof. It should be noted that the use of the machine brings about the same effect of deceleration and consequently the same effect of retraction of the blade, hence a temporary disappearance of the angle of attack and of possibility of power, with possibilities of appearance of pumping phenomena. However, in that case, due to the absorption of the kinetic energy of the rotor by outside use of the power, the effect is more limited and the risk of the propeller becoming pushing is less.
It is an object of the present invention to overcome these drawbacks by providing these aerogenerators or wind-powered engines with particularly simple means for avoiding the tendency of the blade to feather in the event of deceleration of the rotor.
It is a further object of the invention to obtain a better use of the wind whose velocity is less than the nominal speed for which the aerogenerator was designed, an exact control of the speed of rotation of the propeller of the aerogenerator and consequently of
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patent: 2451541 (1948-10-01), Doman
patent: 2638170 (1953-05-01), Prewitt
patent: 3469633 (1969-09-01), Avondoglio
patent: 4083651 (1978-04-01), Cheney, Jr. et al.
patent: 4302152 (1981-11-01), Jensen
patent: 4331881 (1982-05-01), Soderholm et al.
patent: 4352629 (1982-10-01), Cheney, Jr.
Duncanson Jr. W. E.
Groupment d'Interet Economique Aerogenerateurs Carre
Roskoski Bernard
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